1. Field of the Invention
The present invention relates to an actuation device, and more particularly, to an actuation device that uses the driving force resulting from a phase transformation in shape memory alloys.
2. Description of the Related Art
As consumer technology industry keeps its vigorous growth in modern days, all kinds of electronic products making things better and easier for consumers never stop emerging out of the market. On the list of some most widely-used electronic products in recent years, digital cameras and camera cell phones may never be missed.
A prior-art lens module for a digital camera or camera cell phone typically includes a housing, an optical lens and an image sensor. The optical lens for capturing images is coupled to the front side of the housing, wherein the optical lens is generally adjusted through certain mechanism, either of manual or automatic control, so that desired focal lengths can be obtained accordingly.
Said prior-art lens module for digital cameras or camera cell phones are required to be lightweight, thin and small, while at the same time, it needs to be exquisite and durable. Therefore, in a digital camera or camera cell phone, uses of lens modules for focal-length adjustment, which is controlled manually or driven by an electric motor (i.e., linear or non-linear movements), may be restricted due to space or weight limitations. This could further limit zoom ratios or other functions of the optical lens.
Typically, a prior-art lens module is provided with a flat spring that works by balancing with electromagnetism. Nonetheless, flat springs are likely to be deformed by external forces. For example, forces resulting from shocks, resets or continual uses of optical lenses may influence the stability and precision in lens movements. Therefore, there are drawbacks to prior-art lens modules that need to be improved.